Summary:
If a message has only "line", or "line" and "char", we don't point out the location in the context block.
When a message includes "line", show chevrons on the line.
When a message includes "line" and "char", show chevrons on the line and a caret on the next line.
Test Plan: Ran regex linters to capture line, line+char, and normal linters to capture everything. Output appeared sane.
Reviewers: csilvers, vrana, btrahan
Reviewed By: csilvers
CC: aran
Differential Revision: https://secure.phabricator.com/D2642